1. Field of the Invention
The present invention relates to cephem antibiotics useful as pharmaceuticals for human beings and animals.
2. Background Art
Cephem antibiotics possesses excellent antimicrobial activity and low toxicity in mammals and hence are medicaments which are very useful for treatment of infectious diseases of mammals.
The so-called onium salt type cephem antibiotics typified by cefozopran and cefpirome, which have aminothiazolyl (aminothiadiazolyl) acetyl at the 7-position and a quaternary salt substituent at the 3-position, are characterized by having potent antimicrobial activity and a wide spectrum of bacteria from Gram-positive bacteria to Pseudomonas aeruginosa. Therefore, numerous studies and developments in the antibiotics of this type have been made in many countries in the world.
However, even the onium-salt-type cephem compounds, such as cefozopuran and cefpirome, are not always satisfactory in terms of antimicrobial activity against Pseudomonas aeruginosa or Gram-positive bacteria such as Staphylococcus aureus which have brought about a clinical problem in recent years. In addition, infectious diseases caused by methicillin-resistant Staphylococcus aureus (MRSA) or penicillin-resistant streptococcus pneumoniae (PRSP) have been a serious clinical problem these days. It is therefore strongly demanded to obtain novel onium salt type cephem antibiotics which have improved antimicrobial activity also against these bacteria (Chapter 11 by W. E. Wick, "Cephalosporins and Penicillins, Chemistry and Biology" edited by E. H. Flynn, Academic Press, New York, N.Y., 1972; 18.1 "Cephalosporins" by Hatsuo Aoki, "The Leading Studies in Antibiotics" edited by Masaji Ono and Satoshi Omura, Tokyo Kagaku Dojin Kabushiki Kaisha, Japan, 1987; and "Manifestation of Resistance and Molecular Genetics" by Ryoichi Okamoto and Matsuhisa Inoue, "Sogo Rinsho", vol. 42, No. 2, 1993).
In recent years, cephem derivatives having both quaternary ammonium methyl at the 3-position of the cephem ring and 2-(2-aminothiazol-4-yl)- or 2-(5-amino-1,2,4-thiadiazol-3-yl)-2-hydroxy(or substituted hydroxy)iminoacetamide group at the 7-position have been found to possess high antimicrobial activity and stability against .beta.-lactamase, and numerous studies and developments on these cephem derivatives have been made in the art. Among others, cephem compounds having substituted or unsubstituted imidazo[5,1-b]thiazolium-6-yl at the 3-position of the cephem ring are described in WO 95/07912.
However, no compounds having sulfamidoalkyl or substituted sulfamidoalkyl on the imidazo[5,1-b]thiazole ring have been reported so far as the present inventors know.